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Fermi-LAT detection of another rapid GeV flare from the blazar PKS 1510-089

ATel #1897; S. Ciprini (Univ. Perugia & INFN Perugia), S. Corbel (CEA Saclay); on behalf of the Fermi Large Area Telescope Collaboration
on 9 Jan 2009; 19:51 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Stefano Ciprini (stefano.ciprini@pg.infn.it)

Subjects: Gamma Ray, >GeV, AGN, Quasar, Transient

Referred to by ATel #: 1957, 1988, 2033, 3473

The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope (formerly GLAST, launched June 11, 2008), has observed, since January 08, 2009, a rapid flare from a gamma-ray source positionally consistent with the blazar PKS 1510-089 (RA:15h12m50.5329s, Dec:-09d05m59.828s, redshift 0.360 and already known as an EGRET gamma-ray source, 3EG J1512-0849).

Preliminary analysis indicates that the source is in a high state with a gamma-ray flux (E>100MeV) exceeding the pre-defined LAT flaring source reporting threshold of 2x10^-6 photons cm^-2 s^-1.  This is the second time that Fermi is observing and announcing a similar GeV flare in this blazar (September 2008, ATEL#1743) that was also well detected previously in 2008 by AGILE (ATEL#1436). During the first hours of January 09, 2009 there are hints for a fading, but based on the previous gamma-ray behavior monitored by Fermi LAT in the past months, the current activity state and brightness provides chances for further fast flares in the next days. 

This blazar is classified as a Flat Spectrum Radio Quasar (FSRQ), and is rather bright at optical bands, allowing an easier ground-based follow up.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. PKS 1510-089 is one of the "LAT Monitored Sources", and consequently, a preliminary, uncalibrated estimation of the daily gamma-ray flux observed by Fermi LAT is publicly available. In consideration of the ongoing activity of this source we strongly encourage multiwavelength observations. For this source the Fermi LAT contact person is A. Tramacere (tramacer@slac.stanford.edu).

The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.